This invention relates to the co-drying of highly hydrated, relatively inert, carbonate-free aluminum oxyhydroxide suspensions. The suspensions are useful as adsorptive, protein-binding agents. Furthermore, one aspect of this invention relates to resuspendable, adsorptive, protein-binding agents. This invention also concerns topical skin compositions utilizing the agents produced in accordance with this invention.
It is well known to those skilled in the art that aluminum hydroxide gels are irreversibly degraded upon drying. The dehydration processing effectuates the loss of "water-of-constitution", among other entities, resulting in the destruction of most of the positive attributes characteristic of such gels, which properties serve as the very basis of their use in many applications. Illustrative degradative changes which can result are the following:
(1) alteration of the physiochemical structure of the products affecting their surfaces as well as their chemical reactivities;
(2) loss of adsorbent capacity;
(3) impairment of suspendability;
(4) increased density;
(5) increased particle size; and
(6) reduced viscosity.
The degradation of aluminum hydroxide gels upon dilution with water is discussed in "A Vehicle For Stabilizing Aluminum Hydroxide Gel" by Kerkhof, N. J.; Hem, S. L. and White, J. L., JOURNAL OF PHARMACEUTICAL SCIENCES, 75, Vol. 64, No. 12, pp. 2030-2032, Dec. 1975.
U.S. Pat. Nos. 4,112,072 and 4,115,553 are directed to producing dried antacids. These patents describe the codrying of certain basic reactive aluminum bicarbonate-carbonate compounds with polyols to form novel antacid tablets.
U.S. Pat. No. 3,599,150 concerns a freeze stable suspension of an aluminum hydroxide gel. The suspension has an alum-precipitated aqueous extract or aqueous pyridine extract of an antibody producing antigenic substance absorbed thereon in an aqueous solution containing a water-soluble non-toxic polyhydric alcohol and water-soluble non-toxic polymers. This patent, however, is not concerned with co-drying of the aluminum hydroxide gel.
Non-reactive aluminum oxyhydroxides in the wet state, i.e., suspended in water, are known as good adsorbers. For example, such suspensions are used in vaccines as toxin adsorbers (an adsorbent is a material that attracts and holds to its surface a gas, liquid, or solid ). Heretofore, these gels were useful only in the wet state. It was recognized that it was uneconomical to "ship large quantities of water around" with the aluminum hydroxide and that it would be advantageous to concentrate the aluminum hydroxide and resuspend it when needed. Attempts to dry such suspensions in order to concentrate them have heretofore not met with success due to the degradation upon drying of aluminum hydroxide as discussed above.
Heretofore, there has been no teaching of co-drying an inactive aluminum oxyhydroxide gel to produce an adsorptive, protein-binding agent. Furthermore, no such agent has heretofore been produced with sufficient resuspendability properties.